Voyager 1 image of Saturn's moon Dione. With a diameter of 1120 km, Dione is Saturn's fourth largest satellite (after Titan, Rhea, & Iapetus). It orbits Saturn every 65.7 hours. The image, recorded at the time of Voyager 1's encounter with the Saturnian system in November 1980, shows Dione's heavily cratered terrain. Different densities of cratering indicate that there have been episodes of surface renewal since the period of heavy bombardment. Also visible at upper left, near the terminator, are a number of troughs or canyons.